In a cement manufacturing facility, the amount of a volatile component such as chlorine contained in industrial waste has recently increased in a kiln with the increase in the amount of industrial waste to be treated, and thus an adverse influence may be exerted on the quality of cement and the operation of a cement kiln system. Thus, a chlorine bypass device for removing chlorine from the cement manufacturing facility has been disposed so as to cope with the problem.
This chlorine bypass device is a device in which, in order to remove a volatile component such as chlorine concentrated by repeating volatilization and condensation between a cement kiln and a preheater, chlorine bypass dust containing the solidified volatile component composed mainly of a chlorine compound is produced by bleeding an exhaust gas from a kiln tail portion of the cement kiln, followed by cooling, and the chlorine bypass dust is discharged out of the system thereby removing chlorine from the inside of the cement kiln.
The chlorine bypass dust generated in the chlorine bypass device contains a large amount of the chlorine compound and heavy metal. It is necessary to remove the chlorine compound and heavy metal so as to reuse as the cement raw material again.
Thus, a method of removing a chlorine component by washing the chlorine bypass dust with water has been proposed and put into practical use.
For example, there is proposed a method for a treatment of converting into a cement raw material, which comprises the steps of adding water to a waste containing chlorine thereby converting the waste into a slurry; eluting chlorine contained in the waste; filtering the slurry in which chlorine is eluted; optionally washing the slurry to remove chlorine, separating the slurry into a desalted cake and a filtrate through filtration; using the desalted cake as a cement raw material and adding a chelating agent and a pH adjustor to the filtrate, thereby sedimenting heavy metal and a harmful component and removing them; adding additives to the filtrate after the heavy metal and harmful component have been removed, thereby replacing calcium ions by sodium ions; and using calcium carbonate thus sedimented as a cement raw material (refer to Patent Document 1).
There is also proposed, as a method for separating and recovering a chlorine compound removed by washing the waste with water, a method for treating a waste, which comprises the steps of washing a waste with water thereby eluting a chlorine component and a lead component, thus carrying out solid-liquid separation (washing step); adding an alkali solution to the solid removed by filtration thereby eluting the lead component and converting calcium into a hydroxide, followed by removal through filtration (alkali elution step); adding the filtrate to the filtrate separated in the washing step and adding a sulfidizing agent thereby sedimenting and separating lead (deleading step); adding a carbonic acid source to the deleaded filtrate thereby sedimenting and separating calcium (calcium removal step); and heating the filtrate thereby sedimenting a chloride, followed by separation and recovery of the chloride (salt recovery step) (Patent Document 2).
(Patent Document 1)    Japanese Patent No. 3,304,300
(Patent Document 2)    Japanese Unexamined Patent Application, First Publication No. 2003-1218